JPH11306536A - Magnetic tape for computer data recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic tape for computer data recording capable of ameliorating the deficiency of the adhesive force between an arom. polyamide base and a magnetic layer formed thereon and maintaining high traveling durability in spite of long-term preservation. SOLUTION: This magnetic tape is constituted by laminating an adhesive layer consisting of a polymer and the magnetic layer of 1.2 to 2.5 μm in thickness contg. ferromagnetic powder and a binder in this order on the one side of the arom. polyamide base and providing the other side with a back-coating layer and has a total thickness of 4.0 to 8.0 μm. The peeling strength between the adhesive layer and the base is >=95 g/cm and the friction coefft. on the surface of the magnetic layer of the magnetic tape after the magnetic tape is preserved for 30 days under conditions of 60 deg.C and 90% RH does not exceed 0.3. The magnetic tape, of which the amt. of the arom. ester deposited on the surface of the magnetic layer after preservation from the copolymer polyester of the adhesive layer does not exceed 1 mg/m<2> , is also disclosed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape which is advantageously used as an external recording medium for recording computer data.

[0002]

2. Description of the Related Art In recent years, with the spread of office computers such as minicomputers and personal computers, magnetic tapes (so-called backup tapes) for recording computer data as external recording media have been actively studied. . When a magnetic tape for such a purpose is put into practical use, an improvement in the recording capacity of the magnetic tape is strongly demanded, especially in conjunction with the downsizing of the computer and the increase in the information processing capability. In addition, magnetic tapes are used under a wide range of environmental conditions (especially fluctuating temperature and humidity conditions) due to the expansion of the use environment, so the reliability of data storage, especially the data Reliability for performance such as stable recording and reading is demanded more than before.

In general, a magnetic tape has a configuration in which a magnetic layer is provided on a nonmagnetic support made of a flexible material such as a synthetic resin. In order to achieve a large recording capacity (volume recording capacity) as described above, the magnetic powder is reduced by reducing the particle size of the magnetic powder, improving its dispersibility, or making the magnetic layer thinner. It is said that an effective method is to increase the recording density of the layer itself and reduce the total thickness of the magnetic tape. In order to maintain good sensitivity (in particular, output in a high frequency range), the magnetic layer is preferably smooth. However, in order to prevent turbulence due to the smoothing and a decrease in running properties, the magnetic layer is usually used. The backcoat layer is provided on the surface opposite to the magnetic layer.

When the total thickness of the magnetic tape is reduced by using a non-magnetic support having a small thickness, the self-supporting property and strength of the obtained magnetic tape are reduced. For this reason, aromatic polyamides (particularly aramid), which are conventionally known as a material for a non-magnetic support having high rigidity, are advantageously used. However, when aramid is used as a support material, there is a problem that a sufficient adhesion to a magnetic layer (a non-magnetic layer in the case of a multilayer structure) provided thereon cannot be obtained.
Such insufficient adhesion causes peeling or damage of the edge of the magnetic tape during running, and is particularly problematic in a magnetic tape for computer data recording which requires high running durability.

[0005] JP-A-7-282438 discloses a method in which an adhesive layer mainly composed of a polymer is provided on a nonmagnetic support,
There has been proposed a magnetic recording medium (magnetic tape) having a multilayer structure in which a lower coating layer (nonmagnetic layer) and a magnetic layer are laminated thereon. By providing the adhesive layer, even when an aramid support is used, poor adhesion between the support and the layer provided thereon is improved, and a thin magnetic tape provided with good running durability Is obtained. Here, as an example, an adhesive layer made of a polyester resin (polyethylene terephthalate / aromatic linear polyester) having a thickness of 0.1 μm is provided on the aramid support together with the example of the 8 mm video tape having the multilayer structure. An 8 mm video tape having a configuration in which a magnetic layer is further provided directly on the tape is described.

[0006]

A standard for a magnetic tape for computer data recording which has been conventionally used in a digital data recording system is determined for each recording / reproducing system to be used, and is a so-called DLT type, DDS type or D8 type. Types such as types are known. In these types, the tape shape and the recording / reproducing characteristics thereof are standardized corresponding to the recording / reproducing system. For example, DDS type (D
For a magnetic tape compatible with DS-2 type), it is necessary that the reproduction output be able to obtain a predetermined value not only in the short wavelength region but also in the long wavelength region. Generally, it is advantageous to use a thin magnetic layer to increase the reproduction output in the short wavelength region, but to achieve a predetermined reproduction output even in the long wavelength region, it is necessary to increase the thickness of the magnetic layer to some extent. become. For this reason, the thickness of the magnetic layer of this type of magnetic tape is usually 1.2 to 2.
It is set in the range of 5 μm. However, according to the study of the present inventor, if the thickness of the magnetic layer is made relatively thick as described above, even if an adhesive layer made of a polymer as described above is provided, a sufficient adhesion force cannot be obtained. It was found that peeling occurred between the magnetic layer and the magnetic layer, and sufficient running durability could not be obtained.

The present inventor further studied the polymer forming the adhesive layer and the thickness, and found that a polymer having a high adhesive strength such as a copolymerized polyester resin containing terephthalic acid and ethylene glycol as main components was used, and It has been found that the adhesion between the aromatic polyamide support and the magnetic layer can be improved by increasing the coating amount and increasing the thickness of the adhesive layer. However, when the magnetic tape with improved adhesion is stored for a long period of time (particularly under high-temperature and high-humidity conditions), a powdery substance precipitates on the surface of the magnetic layer, which causes It has been found that a new problem occurs in that the friction coefficient of the layer is increased, the running durability is reduced, and the head is easily stained.

An object of the present invention is to improve the insufficient adhesion between the aromatic polyamide support and the magnetic layer formed thereon, and to maintain high running durability even after long-term storage. It is an object of the present invention to provide a magnetic tape for recording computer data.

[0009]

Means for Solving the Problems The present inventors have examined the use of a copolyester resin as an adhesive layer for powdery precipitates that cause a decrease in running performance. According to this, it was found that this powdery substance was due to low molecular components mixed in the copolymerized polyester resin forming the adhesive layer. That is, it was found that when these components excessively exuded on the magnetic layer after storage, they were precipitated as powders (low molecular components such as aromatic esters) there. The low molecular component such as the aromatic ester is a component mixed as a by-product when synthesizing the copolymerized polyester resin constituting the adhesive layer, and is a component that is extremely difficult to remove. And the inventor's further research has found that an organic phosphorus compound is effective for suppressing the precipitation of the powdery substance. It is presumed that the precipitation of the powdery substance is suppressed by the added organic phosphorus compound because the organic phosphorus compound undergoes a cross-linking reaction with the functional group of the low-molecular component, thereby suppressing the progress of the reaction.

According to the present invention, an aromatic polyamide support is laminated on one side with a polymer adhesive layer and a magnetic layer having a thickness of 1.2 to 2.5 μm containing a ferromagnetic powder and a binder in this order. The backing layer is provided on the other side of the support, and in a magnetic tape for computer data recording having a total thickness of 4.0 to 8.0 μm, the peel strength between the adhesive layer and the support is reduced. 95 g / cm or more, and the coefficient of friction of the surface of the magnetic layer of the magnetic tape after storing the magnetic tape at 60 ° C. and 90% RH for 30 days does not exceed 0.3. A computer data recording magnetic tape (first embodiment).

Further, according to the present invention, an adhesive layer made of a thermoplastic saturated high molecular weight polyester containing an aromatic polyester and a ferromagnetic powder and a binder containing a binder on one side of an aromatic polyamide support. A magnetic tape for computer data recording having a magnetic layer of 2 to 2.5 μm and a back coat layer on the other surface of the support and having a total thickness of 4.0 to 8.0 μm. The aromatics having a peel strength of not less than 95 g / cm with respect to a support and being deposited on the surface of the magnetic layer after storing the magnetic tape at 60 ° C. and 90% RH for 30 days. There is also a magnetic tape for computer data recording (second embodiment) characterized in that the amount of the ester does not exceed 1 mg / m ² . In the present specification, the peel strength means 180-degree peel strength (g / cm).

The magnetic tape for recording computer data of the present invention preferably has the following aspects. (1) After storage, the coefficient of friction of the surface of the magnetic layer of the magnetic tape does not exceed 0.25 (more preferably 0.22). (2) The amount of the aromatic ester deposited on the surface of the magnetic layer after storage does not exceed 0.9 mg / m ² . (3) The magnetic layer contains an organic phosphorus compound represented by the following formula (I), (II) or (III).

[0013]

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[In the above formula, R ¹ , R ² and R ³
Represents an independently substituted or unsubstituted alkyl group, alkenyl group or aryl group, and M ¹ , M ² and M ³ are
Each independently represents a hydrogen atom, an alkali metal atom or -N ⁺ (R) ₄
(R represents an alkyl group), and m, n and p
Represents 1 or 2 each independently. (4) In (3), the organic phosphorus compound is phenylphosphonic acid. (5) In (3), the content of the organic phosphorus compound in the magnetic layer is 1.5 to 10 with respect to 100 parts by weight of the ferromagnetic powder.
Parts by weight (more preferably 1.8 to 8 parts by weight, especially 1.8 parts by weight)
-5 parts by weight). (6) The thickness of the adhesive layer is in the range of 0.08 to 0.15 μm (more preferably 0.08 to 0.12 μm). (7) The aromatic polyamide is aramid. (8) The thickness of the magnetic layer is in the range of 1.5 to 2.5 μm. (9) The total thickness of the magnetic tape is in the range of 4.5 to 7.5 μm.

(10) The backcoat layer contains carbon black, the average particle size of which is 10-20 μm, and the average particle size is 230-30 μm.
It is composed of two types of carbon black having different average particle sizes of coarse particle carbon black of 0 μm. (11) The back coat layer contains an inorganic powder, the inorganic powder is a soft inorganic powder having a Mohs hardness of 3 to 4.5 and a Mohr hardness of 5
To 9 hard inorganic powders. (12) The soft inorganic powder is calcium carbonate. (13) The hard inorganic powder is α-iron oxide or α-alumina. (14) The surface roughness Ra of the back coat layer (center line average roughness at a cutoff of 0.08 mm) is 0.0030 to
It is in the range of 0.060 μm.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The magnetic tape for computer data recording of the present invention (hereinafter simply referred to as "magnetic tape") has a total thickness of 4.0 to 8.0 corresponding to the so-called DDS-2 type as described above.
μm (preferably 4.5 to 7.5 μm) magnetic tape, wherein one side of an aromatic polyamide support is provided with an adhesive layer made of a polymer or a thermoplastic saturated high molecular weight polyester containing an aromatic polyester. And an adhesive layer of 1.2 to 2.5 μm (preferably 1.5 to 2.5 μm).
m) and a magnetic layer having a thickness of m) are laminated in this order, and a back coat layer is provided on the other side of the support. In the invention of the first aspect, the peel strength between the adhesive layer and the support is 95 g / cm (preferably 98 g / cm).
After the magnetic tape has been stored at 60 ° C. and 90% RH for 30 days, the coefficient of friction of the surface of the magnetic layer of the magnetic tape is 0.3 (preferably 0.25, more preferably 0.25). 0.22). Further, the invention of the second aspect is characterized in that the peel strength between the adhesive layer and the support is 95 g / cm (preferably 98 g / c
m) or more, and the magnetic tape is heated at 60 ° C. and 90% R
The amount of the aromatic ester deposited on the surface of the magnetic layer after storage for 30 days under the condition of H does not exceed 1 mg / m ² (preferably 0.9 mg / m ² ). Things.

In the magnetic tape according to the present invention, the peel strength between the adhesive layer and the support is maintained at a certain value or more irrespective of the relatively thick magnetic layer.
By including the following organic phosphorus compound, it is possible to suppress the increase in the friction coefficient of the surface of the magnetic layer to a certain value or less even when the magnetic layer is stored for a long period of time. In addition, the amount of the aromatic ester, which is deposited on the surface of the magnetic layer after storage and mixed in the copolymerized polyester, can be suppressed to 1 mg or less per 1 m ² .

First, the organic phosphorus compound used in the present invention will be described in detail. The organic phosphorus compound has the following formula (I) or (II)
Or (III).

[0019]

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In the above formula, as the substituted or unsubstituted alkyl group represented by R ¹ , R ² and R ³ , those having 1 to 22 carbon atoms are preferable. May be. Examples of these include groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, dodecyl, tetradecyl, and octadecyl, 2-aminoethyl, and 2-butoxyethyl. it can. The substituted or unsubstituted alkenyl group may be linear or branched. And examples of these include groups such as vinyl, propenyl, isopropenyl, butenyl, pentenyl, allyl and oleyl. Examples of the substituted or unsubstituted aryl group include phenyl, naphthyl, anthryl, diphenyl, diphenylmethyl, p-
Mention may be made of groups such as ethylphenyl, p-nitrophenyl, tolyl, and xylyl. Further, the aryl group may include a ring other than a benzene ring such as indene or tetralin.

Examples of the alkali metal atom represented by M ¹ , M ² and M ³ include a sodium atom and a potassium atom. Examples of the group represented by -N ⁺ (R) ₄ (R is an alkyl group) include a tetraethylammonium ion. m, n, and p
Represents 1 or 2, respectively.

Examples of the organic phosphorus compound represented by the above formula include mono- and diesters of phosphoric acid and salts thereof, mono- and diesters of phosphorous acid, salts thereof, phosphonic acids and salts thereof, and phosphinic acids And salts thereof. Hereinafter, specific examples of the organic phosphorus compound that can be used in the present invention will be described.

[0023]

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[0024]

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In the above examples, an organic phosphorus compound having an aryl group is preferable, and an organic phosphorus compound having a phenyl group (particularly, phenylphosphonic acid) is more preferable.
It is. In addition, about the said organic phosphorus compound, it describes in Unexamined-Japanese-Patent No. 1-189025, for example.
The organic phosphorus compound is preferably contained in the magnetic layer. The content of the organic phosphorus compound in the magnetic layer is 1.5 to 10 parts by weight (more preferably 1.8 to 8 parts by weight, particularly 1.8 to 5 parts by weight) based on 100 parts by weight of the ferromagnetic powder. Is preferably within the range.

In the magnetic tape of the present invention, an adhesive layer made of a polymer and a magnetic layer containing the above organic phosphorus compound are laminated in this order on an aromatic polyamide support, and a back coat is formed on the opposite surface of the support. A layer is provided. Hereinafter, the support, the adhesive layer, the magnetic layer, and the back coat layer will be described in detail in order.

The aromatic polyamide used for the support material is
It preferably contains a repeating unit represented by the following formula (IV) or (V). — (NH—Ar ¹ —NHCO—Ar ² —CO) — (IV) — (NH—Ar ³ —CO) — (V) Ar ¹ , Ar ² , and Ar ³ each represent an aromatic ring (the aromatic ring is Condensed) or a group containing at least one aromatic ring. Examples of Ar ¹ , Ar ² and Ar ³ include the following.

[0028]

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Here, X and Y represent -O- and-, respectively.
CH ₂ —, —CO—, —SO ₂ —, —S—, and —C
Represents a group selected from (CH ₃ ) ₂ —. The hydrogen atom of the aromatic ring may be substituted. Examples of the group or atom capable of substituting a hydrogen atom of an aromatic ring include a halogen atom (particularly, chlorine), a nitro group, an alkyl group having 1 to 3 carbon atoms (particularly, a methyl group), An alkoxy group can be mentioned. The hydrogen atom of the amide bond which is a constituent component of the polymer may be substituted.

The aromatic polyamide used in the present invention is preferably a polymer having an aromatic ring bonded at the para position occupying 50% or more (more preferably 70% or more) of the total aromatic ring. From the viewpoint of lowering the hygroscopicity, it is preferable that the polymer is a polymer in which an aromatic ring in which a hydrogen atom on an aromatic ring is substituted with a halogen atom (particularly a chlorine atom) accounts for 30% or more of the whole. In addition, about the said aromatic polyamide, it describes in Unexamined-Japanese-Patent No. 8-55327 or 8-55328. In the present invention, it is preferable to use aramid (a wholly aromatic polyamide). A typical example of aramid products is Microtron (Toray Industries, Inc.)
Manufactured by Asahi Kasei Kogyo Co., Ltd.). The thickness of the support made of an aromatic polyamide used in the present invention is 1.5 to 5.5 μm (more preferably, 3.0 to 5.5 μm).
It is preferably in the range of 5.0 μm, particularly 3.5 to 5.0 μm.

The adhesive layer is a layer made of a solvent-soluble polymer. Preferred polymers include polyester polyurethane, polyether polyurethane, polyester, butadiene-acrylonitrile copolymer, styrene-butadiene copolymer and the like, and these polymers include sulfonic acid groups (including those converted into alkali metal salts). A hydrophilic polar group may be included. The polymer for the adhesive layer used in the present invention is provided so that the above-described polymer is sandwiched between two aromatic polyamide supports, and the two supports are separated by a 180-degree peel tester. The peel strength at this time is selected from those having a peel strength of 80 g / cm or more.

Particularly preferred polymers in the present invention are aromatic dicarboxylic acids (eg, terephthalic acid, isophthalic acid)
And aromatic diols (eg, ethylene glycol, diethylene glycol, propylene glycol). At this time, the aromatic dicarboxylic acid having a hydrophilic polar group such as sulfoisophthalic acid in a part of the aromatic dicarboxylic acid is used in a desired amount (preferably, the polar group is 0.05 to 0). It is particularly preferable to use them together. The molecular weight of such an aromatic polyester is preferably 24,000 to 28,000 in number average molecular weight, but is usually in the range of 0.5% by weight, and the number average molecular weight is 8%.
It contains no more than 00 aromatic esters. The adhesive layer
It can be formed by applying a polymer solution on a support. The thickness of the adhesive layer is usually 0.08 to 0.1.
The range is 5 μm (more preferably, 0.08 to 0.12 μm).

The magnetic layer is composed of a ferromagnetic powder and a binder. Further, the magnetic layer usually further contains carbon black as a lubricant or conductive powder, and an abrasive. Examples of the ferromagnetic powder that can be used for the magnetic layer include γ-Fe ₂ O ₃ , Fe ₃ O ₄ , and FeOx.
(X = 1.33-1.5), CrO ₂ , Co-containing γ-F
e ₂ O _3, Co-containing FeOx (x = 1.33~1.
5), ferromagnetic metal powder, and plate-like hexagonal ferrite powder. In the present invention, a ferromagnetic metal powder or a plate-like hexagonal ferrite powder is preferably used as the ferromagnetic powder, and a ferromagnetic metal powder is particularly preferable.

The ferromagnetic metal powder preferably has a particle specific surface area of preferably 30 to 70 m ² / g and a crystallite size determined by X-ray diffraction of 50 to 300 A. If the specific surface area is too small, it will be difficult to sufficiently cope with high-density recording, and if it is too large, dispersion will not be sufficient, and it will be impossible to form a magnetic layer with a smooth surface. It becomes difficult. The ferromagnetic metal powder contains at least Fe. Specifically, Fe, Fe-Co, Fe-Ni, Fe-Zn-N
It is a metal simple substance or an alloy mainly composed of i or Fe-Ni-Co. Regarding the magnetic properties of these ferromagnetic metal powders, in order to achieve a high recording density, the saturation magnetization (saturation magnetic flux density) (σs) is usually 110 emu / g.
Or more, preferably 120 emu / g or more, 170 emu
/ G or less. The coercive force (Hc) is 1800 to 280
It is preferably in the range of 0 Oersted (Oe).
The major axis length of the powder (that is, the average particle diameter) determined by a transmission electron microscope is usually 0.5 μm or less, preferably 0.01 to 0.3 μm, and the axial ratio (major axis length / minor axis length,
Needle ratio) is 5 or more and 20 or less, preferably 5 to 15
It is. In order to further improve the properties, B, C,
Non-metals such as Al, Si and P, or salts and oxides thereof may be added. Usually, an oxide layer is formed on the particle surface of the metal powder for chemical stability.

In the present invention, a particularly preferred ferromagnetic metal powder contains Fe as a main component, and further contains Co in an amount of 10 to 40 atomic% (more preferably 20 to 4 atomic%) based on the amount of Fe.
0 atomic%), Al is 2 to 20 atomic% (more preferably 6 atomic%).
-17 atomic%), and 1-15 atomic% (more preferably 2-8 atomic%) of Y. The average major axis length is 0.05 to 0.19 μm (more preferably, 0.1 to 0.19 μm).
05 to 0.15 μm, a particularly preferred range is 0.06 to
0.1 μm). The crystallite size is 100 to 230 angstroms (more preferably 120 to 220 angstroms, particularly preferably 16 to 220 angstroms).
0 to 200 angstroms).
More preferably, the coercive force is between 2000 and 2500 Oe.

The ferromagnetic metal powder which is particularly preferred in the present invention is preferably in the form of a spindle. The spindle-shaped ferromagnetic alloy powder can be synthesized by reducing spindle-type goethite. More specifically, an aqueous solution of a ferrous salt such as ferrous sulfate is reacted with an aqueous solution of an alkali carbonate such as ammonium carbonate in a pH range of 5 to 8 to obtain a suspension containing an iron-containing precipitate. The suspension is subjected to 40 in a non-oxidizing atmosphere.
Ripen at a temperature of ６０60 ° C. for a period of 2 to 7 hours. An aqueous solution of a cobalt salt such as cobalt sulfate or cobalt nitrate is added to the suspension immediately before the start of the aging step, or during the aging step. In addition, a part of the aqueous solution of the cobalt salt may be added to the aqueous solution of the ferrous salt in advance. Thereafter, air is blown into this suspension to cause an oxidation reaction, thereby preparing spindle-shaped goethite particles containing Co. The goethite particles are separated by filtration, washed with water, filtered and then suspended in water.Additionally, a cobalt salt such as cobalt acetate is added if necessary, and an aqueous solution of an aluminum salt such as aluminum sulfate is added. At least one selected from an aqueous solution of sodium silicate such as water glass and an aqueous solution of boric acid is added. In addition, at least a part of these aqueous solutions may be added during the oxidation reaction step in the above goethite preparation process.

Next, if necessary, the pH of the suspension is adjusted.
After adding a known organic polymer flocculant, the mixture is filtered with a filter press and an Oliver filter, and the obtained cake is further granulated and formed, and then dried. Then
This is heat-treated in air at a temperature in the range of, for example, 250 to 500 ° C., to obtain hematite particles. Then, after reducing by heating at a temperature of 300 to 550 ° C. with hydrogen gas, an oxidation treatment for covering the particle surface with an oxide film is performed.
In this oxidation treatment, the above-described heat-reduced metal alloy particles in a molded state are immersed in an organic solvent, and an oxygen-containing gas such as air is blown into the metal alloy particles. There is a method of oxidizing by exposing the metal alloy particles of the above to an atmosphere of an oxygen gas and an inert gas while adjusting the partial pressure of the oxygen gas. The latter method is preferable.

The plate-like hexagonal ferrite powder has a specific surface area of 25 to 65 m ² / g and a plate-like ratio (plate diameter /
Plate thickness) is 2 to 15, particle size (plate diameter) is 0.02 to
It is preferably in the range of 1.0 μm. For the same reason as the ferromagnetic metal powder, high-density recording becomes difficult even if the particle size of the plate-like hexagonal ferrite powder is too large or too small. Plate-like hexagonal ferrite is a ferromagnetic material having a flat shape and an easy axis of magnetization in a direction perpendicular to the plane of the plate, and specifically, barium ferrite, strontium ferrite, lead ferrite, calcium ferrite, and the like. Cobalt substitution products and the like can be mentioned. Of these, cobalt-substituted barium ferrite and cobalt-substituted strontium ferrite are particularly preferred.
The plate-like hexagonal ferrite used in the present invention may further include In, Zn, Ge, N
Elements such as b and V may be added. Regarding the magnetic properties of these plate-like hexagonal ferrite powders, the saturation magnetization (σs) is preferably 50 emu / g or more, more preferably 53 emu / g or more, in order to achieve high recording density. Further, the coercive force (Hc) is preferably in the range of 700 to 2000 Oe (Oe), and more preferably in the range of 900 to 1600 (Oe).

The water content of the ferromagnetic powder described above is 0.0
The content is preferably in the range of 1 to 2% by weight. It is preferable to optimize the water content depending on the type of the binder. The pH of the ferromagnetic powder is preferably optimized by a combination with a binder to be used, and the pH is usually in the range of 4 to 12, and preferably in the range of 5 to 10. The ferromagnetic powder preferably has at least a part of its surface coated with Al, Si, P, or an oxide thereof, if necessary. When using surface treatment,
Usually, it is 0.1 to 10% by weight based on the ferromagnetic powder.
Since the ferromagnetic powder coated in this manner can suppress the adsorption of a lubricant such as a fatty acid to 100 mg / m ² or less, a desired effect can be achieved even if the addition of the lubricant to the magnetic layer is reduced. Soluble Na, Ca, F is contained in the ferromagnetic metal powder.
e, Ni, Si and the like may be contained as inorganic ions, but the content is preferably as small as possible. Usually, if it is 5000 ppm or less, there is no influence on the characteristics.

The lubricant is added to alleviate the friction between the surface of the magnetic layer and the magnetic head by oozing out on the surface of the magnetic layer, and to maintain a smooth sliding contact state. Examples of the lubricant include fatty acids and fatty acid esters. As fatty acids, for example, acetic acid, propionic acid,
Aliphatic carboxylic acids such as 2-ethylhexanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, arachinic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, and palmitooleic acid or a mixture thereof Mixtures can be mentioned.

Examples of the fatty acid ester include butyl stearate, sec-butyl stearate, isopropyl stearate, butyl oleate, amyl stearate, 3-methylbutyl stearate, 2-ethylhexyl stearate, and 2-hexyldecyl. Stearate,
Acyl butyl palmitate, 2-ethylhexyl myristate, a mixture of butyl stearate and butyl palmitate, oleyl oleate, butoxyethyl stearate, 2-butoxy-1-propyl stearate, dipropylene glycol monobutyl ether with stearic acid And various ester compounds or mixtures of glycerol oleate and the like, and diethylene glycol dipalmitate, hexamethylenediol acylated with myristic acid to form a diol, and glycerin oleate. The above fatty acids and fatty acid esters can be used alone or in combination of two or more compounds. The usual content of the lubricant in the magnetic layer is preferably in the range of 0.2 to 20 parts by weight (more preferably, 0.5 to 10 parts by weight) based on 100 parts by weight of the ferromagnetic powder. .

[0042] Carbon black, various such reduction in surface resistivity of the magnetic layer (R _s), reduction of the dynamic friction coefficient (mu _k value), improvement of running durability, and the smooth surface of the magnetic layer to ensure It is added for the purpose of. Carbon black has an average particle diameter of 5 to 350 mμ (more preferably, 10 to 350 mμ).
It is preferably in the range of 300 mμ). The specific surface area is 5 to 500 m ² / g (more preferably, 50
３００300 m ² / g). The DBP oil absorption of carbon black is 10 to 1000 ml / 100.
g (more preferably, 50 to 300 ml / 100 g). The pH is 2 to 10, the water content is 0.1 to 10%, and the tap density is 0.1.
1 g / cc is preferred.

Carbon black obtained by various production methods can be used. Examples of carbon black that can be used include furnace black, thermal black, acetylene black, channel black and lamp black. Specific examples of carbon black products include BLACKPEARLS 2000, 1
300, 1000, 900, 800, 700, VULC
AN XC-72 (above, manufactured by Cabot Corporation), # 35,
# 50, # 55, # 60 and # 80 (all manufactured by Asahi Carbon Co., Ltd.), # 3950B, # 3750B, # 3250
B, # 2400B, # 2300B, # 1000, # 90
0, # 40, # 30, and # 10B (all manufactured by Mitsubishi Chemical Corporation), CONDUCTEX SC, RAVEN,
150, 50, 40, 15 (all manufactured by Columbia Carbon Co., Ltd.), Ketjen Black EC, Ketjen Black ECDJ-500 and Ketjen Black ECDJ-
600 (all manufactured by Lion Aguso Co., Ltd.).

The usual addition amount of carbon black to the magnetic layer is 0.1 to 30 parts by weight based on 100 parts by weight of the ferromagnetic powder.
It is preferably in the range of parts by weight (more preferably 0.2 to 15 parts by weight).

Examples of the abrasive include fused alumina,
Silicon carbide, chromium oxide, corundum, artificial corundum,
Examples include diamond, artificial diamond, garnet, and emery (main components: corundum and magnetite). These abrasives have a Mohs hardness of 5 or more (preferably 6 or more) and an average particle diameter of 0.05 to 1 μm.
(More preferably, 0.2 to 0.8 μm). The usual amount of abrasive added is 1 ferromagnetic powder.
It is preferably in the range of 3 to 25 parts by weight (more preferably 3 to 20 parts by weight) based on 00 parts by weight.

Examples of the binder for the magnetic layer include a thermoplastic resin, a thermosetting resin, a reactive resin, and a mixture thereof. Examples of thermoplastic resins include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid,
Acrylic acid, acrylic acid ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic acid ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, and a homopolymer or a copolymer containing vinyl ether as a structural unit may be mentioned. it can. Examples of the copolymer include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylate-acrylonitrile copolymer, and acrylate-vinylidene chloride copolymer. Polymer, acrylate-styrene copolymer, methacrylate-acrylonitrile copolymer, methacrylate-vinylidene chloride copolymer, methacrylate-styrene copolymer, vinylidene chloride-acrylonitrile copolymer Butadiene-acrylonitrile copolymer, styrene-butadiene copolymer, and chlorovinyl ether-acrylate copolymer.

In addition to the above, polyamide resins, cellulose resins (cellulose acetate butyrate, cellulose diacetate, cellulose propionate, nitrocellulose, etc.), polyvinyl fluoride, polyester resins, polyurethane resins, various rubber resins Etc. can also be used.

Examples of the thermosetting resin or the reactive resin include, for example, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, acrylic reaction resin, formaldehyde resin, silicone resin, and epoxy resin. Examples thereof include a polyamide resin, a mixture of a polyester resin and a polyisocyanate prepolymer, a mixture of a polyester polyol and a polyisocyanate, and a mixture of a polyurethane and a polyisocyanate.

Examples of the above polyisocyanate include tolylene diisocyanate, 4-4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, naphthylene-1,
Examples include isocyanates such as 5-diisocyanate, o-toluidine diisocyanate, isophorone diisocyanate, and triphenylmethane triisocyanate, products of these isocyanates and polyalcohols, and polyisocyanates formed by condensation of isocyanates. .

The binder for the magnetic layer is a vinyl chloride resin, a vinyl chloride-vinyl acetate copolymer, a vinyl chloride-vinyl acetate-vinyl alcohol copolymer, a vinyl chloride-vinyl acetate-maleic anhydride copolymer, and a nitro resin. It is preferable that the resin be composed of a combination of at least one resin selected from cellulose and a polyurethane resin, or a combination of these and a polyisocyanate.
The polyurethane resin is a polyester polyurethane,
Known materials having a structure such as polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used.

Further, for example, JP-A-7-50010 or JP-A-7-282435 has a high glass transition temperature (Tg) (Tg: preferably 40 to 15).
0 ° C, more preferably 70-140 ° C, especially 100-1
(30 ° C.) It is also preferable to use a polyurethane resin or a polyurethane urea resin. By using such a resin as a part of the binder, a high coating film strength can be obtained, and the Young's modulus in the longitudinal direction of the magnetic tape can be increased. Specifically, these resins are polyurethane resins formed by the reaction of a short-chain diol having a weight-average molecular weight of 50 to less than 500 (preferably 62 to 300) with a diisocyanate, or this short-chain diol and an average molecular weight of 50 to 50. It is preferably a polyurethane urea resin formed by the reaction of a short-chain diamine having a molecular weight of less than 500 (preferably 62 to 300) with a diisocyanate.

In order to obtain better dispersibility and durability of the obtained layer, the binder may optionally have -COOM,
_{-SO 3 M, -OSO 3 M,} -P = O (OM) 2, -O
_{-P = O (OM) 2,} (M is a hydrogen atom or an alkali _{metal.) - OH, -NR 2,} -N + R 3 (. R is representative of a hydrocarbon group), epoxy group, -SH And at least one polar group selected from —CN and the like is preferably introduced by copolymerization or addition reaction. Such a polar group is preferably introduced into the binder in an amount of 10 ^-1 to 10 ^-8 mol / g (more preferably, 10 ^-2 to 10 ^-6 mol / g).

The binder in the magnetic layer is usually 5 to 50 parts by weight (preferably 10 to 50 parts by weight) based on 100 parts by weight of the ferromagnetic powder.
30 parts by weight). When a vinyl chloride resin, a polyurethane resin, and a polyisocyanate are used in combination as a binder in the magnetic layer, the vinyl chloride resin is 5 to 70% by weight, and the polyurethane resin is 2 to 50% by weight in all the binders. % And the polyisocyanate is preferably present in an amount ranging from 2 to 50% by weight.

A back coat layer is provided on the other side of the aromatic polyamide support. Generally, a magnetic tape for recording computer data as in the present invention is required to have a higher repetitive running property than a video tape and an audio tape. In order to maintain such high running durability, the back coat layer is preferably formed from carbon black and a binder. Furthermore,
It is preferable that a soft inorganic powder having a Mohs hardness of 3 to 4.5 and a hard inorganic powder having a Mohs hardness of 5 to 9 are included as the inorganic powder. The back coat layer having such a configuration is described in, for example, Japanese Patent Application Laid-Open No. 9-115134.

It is preferable to use two types of carbon blacks having different average particle sizes in combination. In this case, fine carbon black having an average particle size of 10 to 20 μm and an average particle size of 230 to 30
It is preferable to use a combination of 0 μm coarse carbon black. In general, the surface electric resistance of the back coat layer can be set low and the light transmittance can be set low by the addition of the fine carbon black as described above. Some magnetic recording devices use the light transmittance of a magnetic tape and use it for an operation signal. In such a case, the addition of fine carbon black is particularly effective. In addition, fine particulate carbon black generally has excellent holding power for liquid lubricants.
It contributes to a reduction in friction coefficient. On the other hand, when the particle size is 23
Coarse-particle carbon black having a particle size of 0 to 300 μm has a function as a solid lubricant, and forms fine projections on the surface of the back coat layer to reduce the contact area with the guide pole, thereby reducing the friction coefficient. Contribute to reduction.

Specific products of the particulate carbon black include the following. RAVE
N2000B (18mμ), RAVEN 1500B (1
7mμ) (all manufactured by Columbia Carbon Co., Ltd.), BP80
0 (17mμ) (Cabot), PRINTEX9
0 (14mμ), PRINTEX95 (15mμ), P
RINTEX85 (16mμ), PRINTEX75
(17 mμ) (all manufactured by Degussa), # 3950 (16
mμ) (manufactured by Mitsubishi Chemical Corporation). Examples of specific products of coarse particle carbon black include thermal black (270 mμ) (manufactured by Kerncarb) and RAVEN M.
TP (275 mμ) (manufactured by Columbia Carbon Co., Ltd.) can be mentioned.

In the case of using two types having different average particle sizes in the back coat layer, 10 to 20 μm
Is preferably in the range of 98: 2 to 75:25, and more preferably 95: 5. ８５85: 15. The content (total amount) of carbon black in the back coat layer is usually 3 parts per 100 parts by weight of the binder.
0 to 80 parts by weight, preferably 45 to 65 parts by weight.
It is in the range of parts by weight.

The back coat layer has a Mohs hardness of 3 to 3.
By adding the soft inorganic powder of 4.5, the friction coefficient can be stabilized by repeated running. In addition, with the hardness in this range, the sliding guide pole is not scraped. The average particle size of the inorganic powder is 30 to 50 m.
It is preferably in the range of μ. Mohs hardness is 3-4.
Examples of the soft inorganic powder of 5 include calcium sulfate,
Examples include calcium carbonate, calcium silicate, barium sulfate, magnesium carbonate, zinc carbonate and zinc oxide. These can be used alone or in combination of two or more. Of these, calcium carbonate is particularly preferred. The content of the soft inorganic powder in the back coat layer was 1 to 100 parts by weight of carbon black.
It is preferably in the range of 0 to 140 parts by weight, more preferably in the range of 35 to 100 parts by weight.

The back coat layer has a Mohs hardness of 5
By adding the hard inorganic powders of Nos. To 9, the strength of the back coat layer is enhanced, and the running durability is improved. When these hard inorganic powders are used together with carbon black or calcium carbonate, the back coat layer is less deteriorated even by repeated sliding, and becomes a strong back coat layer. Also, the addition of the hard inorganic powder generates an appropriate polishing force, and reduces the adhesion of shavings and the like to the tape guide pole and the like. In particular, when used in combination with calcium carbonate, the sliding characteristics with respect to a guide pole having a rough surface are improved, and the friction coefficient of the back coat layer can be stabilized. The hard inorganic powder used in the present invention has an average particle size of 80 to 250 mμ.
(More preferably, 100 to 210 mμ).

Examples of the hard inorganic powder having a Mohs hardness of 5 to 9 include α-iron oxide, α-alumina, and chromium oxide (Cr ₂ O ₃ ). These powders may be used alone or in combination. Of these, α-iron oxide or α-alumina is preferred. The content of the hard inorganic powder is usually 3 to 30 parts by weight, preferably 3 to 20 parts by weight, based on 100 parts by weight of carbon black.

When the soft inorganic powder and the hard inorganic powder are used in combination in the back coat layer, both are selected and used so that the difference in hardness is 2.5 or more (more preferably 3 or more). Is preferred.

The back coat layer may contain two types of inorganic powders having different specific Mohs hardnesses, each having a specific average particle size, and two types of carbon black having different average particle sizes. preferable. In particular, in this combination, it is preferable that calcium carbonate is contained as the soft inorganic powder. The two inorganic powders having different Mohs hardnesses having a specific average particle size in the back coat layer, and the content ratio (weight ratio) of the two types of carbon blacks having different average particle sizes,
The former: the latter is preferably in the range of 70:30 to 30:70, and more preferably 65:35 to 35:65.
In the range. The thickness of the back coat layer is usually 0.1 to
It is in the range of 1.5 μm (preferably 0.2 to 1.2 μm, more preferably 0.3 to 1.0 μm).

As the binder for the back coat layer, those described as the binder for the magnetic layer can be used. The binder in the back coat layer is usually 5 to 250 parts by weight (preferably 10 to 100 parts by weight based on 100 parts by weight of carbon black).
To 200 parts by weight).

A dispersant can be added to the coating solution for forming each layer of the magnetic tape in order to disperse the magnetic powder and the non-magnetic powder in the binder. If necessary, a plasticizer, conductive particles (antistatic agent) other than carbon black, an antifungal agent, and the like can be added to each layer. Examples of the dispersant include, for example, those having 12 carbon atoms such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, elaidic acid, linoleic acid, linolenic acid, and stearolic acid.
~ 18 fatty acids (RCOOH, R represents 11 to 17 carbon atoms)
An alkyl group or an alkenyl group), a metal soap comprising an alkali metal or an alkaline earth metal of the above fatty acid,
Fluorine-containing compounds of the above fatty acid esters, amides of the above fatty acids, polyalkylene oxide alkyl phosphates, lecithin, trialkylpolyolefinoxyquaternary ammonium salts (alkyl has 1 to 5 carbon atoms)
Individual olefins include ethylene, propylene, etc.), sulfates, and copper phthalocyanine.
These may be used alone or in combination. In the present invention, it is preferable to use copper oleate, copper phthalocyanine, and barium sulfate in combination.
The dispersant is preferably added in any layer in an amount of 0.5 to 20 parts by weight based on 100 parts by weight of the binder.

The magnetic tape can be manufactured by forming an adhesive layer and a magnetic layer on one side of the support and a back coat layer on the other side in this order according to a usual method. The back coat layer preferably has a surface roughness Ra (center line average roughness with a cutoff of 0.08 mm) in the range of 0.0030 to 0.060 μm. Outside this range, the surface state of the back coat layer is transferred to the surface of the magnetic layer in a state in which the magnetic tape is wound, which easily affects the reproduction output and the coefficient of friction with respect to the guide pole. In addition, the adjustment of the surface roughness Ra is usually performed by applying and forming a back coat layer.
In the surface treatment step using a calender roll, it is performed by adjusting the material of the calender roll to be used, its surface properties, pressure and the like.

[0066]

The present invention will be described more specifically with reference to the following Examples and Comparative Examples. The “parts” shown below are
Represents "parts by weight".

Example 1 A coating liquid for forming an adhesive layer having the following composition (concentration: on the surface of a 4.4 μm-thick aromatic polyamide support (aramid; trade name: Microtron, manufactured by Toray Industries, Inc.) 2% by weight) and the thickness after drying is 0.1 μm
And dried, and then a coating liquid for forming a magnetic layer having the following composition having a thickness of 1.8 μm after drying.
m and dried.

After the above steps were completed, a coating solution for forming a back coat having the following composition was applied to the opposite surface of the support so that the thickness after drying was 1.0 μm, and the coating was dried. In this way, the magnetic layer on one side of the support via the adhesive layer,
And the magnetic recording laminated body roll which each has a back coat layer on the other surface was obtained. The obtained magnetic recording laminate roll was subjected to a calender treatment. Next, after the calendering treatment, the magnetic recording laminate roll was slit to a width of 3.8 mm and subjected to a surface polishing treatment to obtain a magnetic tape according to the present invention. The surface roughness Ra (center line average roughness with a cutoff of 0.08 mm) of the back coat layer of the obtained magnetic tape was 0.04 μm.

(Composition of Coating Liquid for Forming Adhesive Layer) 784 parts of cyclohexane 196 parts of methyl ethyl ketone Aromatic polyester [isophthalic acid (*) / ethylene glycol / diethylene glycol = 100/78/22 (molar ratio), number average molecular weight = 25,000, number It contains 0.2% by weight of a component having an average molecular weight of 800 or less (mainly aromatic ester). (*) The sodium salt of sulfoisophthalate was used in an amount of 0.2 mi equivalent / g in the aromatic polyester.

(Composition of Magnetic Layer Forming Coating Solution) Ferromagnetic metal powder (Fe—Co alloy) 100 parts (Co content: 25% by weight, Al content: 10% by weight Y content: 5% by weight) Hc: 1850 Oe, σs: 130 emu / g, S _BET : 58 m ² / g) Vinyl chloride copolymer resin 10 parts (MR-110, manufactured by Zeon Corporation) Polyurethane resin (polyester polyurethane containing sulfonic acid group) 4 Part (manufactured by Toyobo Co., Ltd.) Polyisocyanate 4 parts (Coronate 3041, manufactured by Nippon Polyurethane Industry Co., Ltd.) Carbon black (Asahi Carbon Black # 50) 1 part Abrasive: α-alumina (HIT55, Sumitomo Chemical Co., Ltd.) 12 parts Chromium oxide (G5, manufactured by Nippon Chemical Industry Co., Ltd.) 1 part Organic phosphorus compound (phenylphosphonic acid) 3 parts Oleic acid 0.4 part Listinic acid 0.8 parts Butyl diglycol stearate palmitate 1.2 parts Isoamyl stearate 0.2 parts Methyl ethyl ketone 170 parts Cyclohexanone 50 parts Toluene 80 parts

(Composition of Coating Liquid for Forming Back Coat Layer) 100 parts of fine carbon black powder (BP-800, manufactured by Cabot Corporation, average particle size: 17 mμ) 10 parts of coarse carbon black powder (thermal black, manufactured by Kahn Carb) , Average particle size: 270 mμ) Calcium carbonate 80 parts (Shiraishi Kogyo Co., Ltd., white luster O, average particle size: 40 mμ, Mohs hardness: 3.0) α-alumina 15 parts (Sumitomo Chemical Co., Ltd., HIT55) , Average particle size: 200 mμ, Mohs hardness: 8.5) Nitrocellulose resin 140 parts Polyurethane resin 15 parts Polyisocyanate 40 parts Polyester resin 5 parts Dispersant: copper oleate 5 parts Copper phthalocyanine 5 parts Barium sulfate 5 parts Methyl ethyl ketone 2100 parts Butyl acetate 300 parts Toluene 00 parts

[Example 2] In Example 1, instead of the sulfonic acid group-containing polyester polyurethane resin in the magnetic layer, a polyurethane resin obtained by synthesizing a short-chain diol having a weight average molecular weight of 240 and an organic diisocyanate (glass (Transition temperature: 130 ° C.) except that a sample was prepared in the same manner. Backcoat layer surface roughness R
a was the same as the tape of Example 1.

Comparative Example 1 A sample was prepared in the same manner as in Example 1, except that the concentration of the coating solution for forming an adhesive layer was changed to 1% by weight, and this was used to form an adhesive layer.

Comparative Example 2 A sample was prepared in the same manner as in Example 1, except that the concentration of the coating solution for forming an adhesive layer was changed to 4% by weight, and this was used to form an adhesive layer.

Comparative Example 3 A sample was prepared in the same manner as in Example 1, except that no organic phosphorus compound (phenylphosphonic acid) was added to the magnetic layer.

Comparative Example 4 In Example 1, the addition amount of the organic phosphorus compound (phenylphosphonic acid) in the magnetic layer was 3
A sample was prepared in the same manner except that one part was changed from one part.

Comparative Example 5 A sample was prepared in the same manner as in Example 1, except that the thickness of the magnetic layer was changed from 1.8 μm to 0.5 μm.

Comparative Example 6 A sample was prepared in the same manner as in Example 1, except that the thickness of the magnetic layer was changed from 1.8 μm to 3 μm.

[Evaluation of Performance as Magnetic Tape] (1) Measurement of Peel Strength (g / cm) Between Adhesive Layer and Support The magnetic layer side of a magnetic tape (sample) slit to a 3.8 mm width was measured. Stick the magnetic layer side down with adhesive tape,
The support was peeled off in a 180 ° peel test at 23 ° C. and 70% RH, and the measured value was taken as the peel strength (g / cm).

Each of the obtained samples was subjected to a temperature of 60 ° C. and a humidity of 9
It was stored for 30 days under the condition of 0% RH. After storage, the friction coefficient of the magnetic layer of the obtained magnetic tape was measured by the following procedure. In addition, powdery substances deposited on the magnetic layer of the magnetic tape were quantified by the following method. Further, the performance (running performance, reproduction output) of the magnetic tape was also evaluated. The storage conditions (stored at 60 ° C. and 90% RH for 30 days) specified by the present invention are as follows: The magnetic tape is stored for a long time (normal temperature,
(About 5 years or more under the condition of normal humidity) means a storage condition required to realize a state almost equivalent to a state after a short period of time.

(2) Measurement of friction coefficient The magnetic tape after storage was wound around a cylinder of an actual machine running system (DAT, DAT deck made by Sony Corporation: DTC-77ES) with a tension (T1) of 10 g and an angle of 180 degrees. Then, the tension (T2) required for running the magnetic tape at a speed of 8 mm / sec was measured in the state where the magnetic tape was brought into contact with the magnetic tape. Using these measured values, the coefficient of friction was determined by the following formula.
Coefficient of friction (μ) = 1 / π · ln (T2 / T1)

(3) Measurement of Deposit Amount It was confirmed that the powdery substance deposited on the magnetic layer was an aromatic ester. The amount of the precipitation was measured by the following method. The magnetic tape after storage was set using a DAT deck such that a sapphire blade was in contact with the surface of the magnetic layer, and the tape was full length (length: 120 m, width: 3.8 m)
m), and the powder accumulated on the sapphire blade was sampled and quantified. In addition, the amount of precipitation was shown by the amount per 1 m ² of the magnetic layer surface of the magnetic tape.

(4) Evaluation of Damage on Magnetic Tape after Running The running was repeated 100 times on a DAT deck, and the occurrence of damage to the magnetic layer surface and edges of the magnetic tape after running and the adhesion of dirt on the magnetic layer surface were evaluated. Observed visually and with a microscope,
The following ranking was used for evaluation. A: Almost no occurrence of damage and no contamination on the surface of the magnetic layer are observed. B: Damage was generated and adhesion of dirt on the surface of the magnetic layer was slightly observed. C: The occurrence of damage and adhesion of dirt on the magnetic layer surface are remarkable.

(5) Evaluation of dirt on the magnetic head after running The running was repeated 100 times on the DAT deck, and the state of adhesion of dirt on the surface of the magnetic head after running was visually observed and evaluated by the following ranking. . A: Almost no adhesion of dirt on the magnetic head surface is observed. B: Slight adhesion of dirt on the magnetic head surface was observed. C: Adhesion of dirt on the magnetic head surface is remarkable.

(6) Evaluation of Measurement of Reproduction Output 3000 ftpmm (Flux tramm
nsition per mm; the number of magnetization reversal wavelengths per 1 mm) and a signal having a unit recording density of 83.3 ftpmm were recorded at an optimum recording current, and the reproduction output was measured. The output value was shown as a relative value with the reproduction output of Example 1 being 100. In addition, in the official standard ISO (13923),
It is required that a reproduction output value when a signal having a unit recording density of 3000 ftpmm and 83.3 ftpmm is recorded at an optimum recording current is in the range of 80 to 126. Table 1 shows the evaluation results.

[0086]

[Table 1]

From the results shown in Table 1 above, in the case of the sample in which phenylphosphonic acid was added to the magnetic layer (Examples 1 and 2), the powdery substance (aromatic ester) deposited on the surface of the magnetic layer after storage was reduced. It can be seen that the amount can be reduced, so that the increase in the friction coefficient on the surface of the magnetic layer is suppressed, and good running performance can be obtained. Also, the reproduction output can obtain a value conforming to the standard.

On the other hand, as in Comparative Example 1, in the case of the sample in which the amount of the polymer forming the adhesive layer was reduced (ie, the thickness of the adhesive layer was reduced), the distance between the adhesive layer and the support was small. It can be seen that sufficient adhesion strength cannot be obtained, so that the running performance is reduced. Conversely, in the case of a sample in which the amount of the polymer forming the adhesive layer was increased (the thickness of the adhesive layer was increased) (Comparative Example 2), despite the addition of phenylphosphonic acid, The deposition amount of the powdery substance increased, and as a result, the friction coefficient also increased, and the head dirt became remarkable. Further, in the case of a sample in which phenylphosphonic acid is not added or the amount of phenylphosphonic acid added is small as in Comparative Examples 3 and 4, the amount of powdery substances deposited increases, and as a result, friction is increased. The coefficient also increased, and head contamination became remarkable. As can be seen from Comparative Examples 5 and 6, in the case of a sample in which the thickness of the magnetic layer is extremely thin or conversely, the reproduction output value is more likely to fluctuate than the sample of Example 1, Further, it can be seen that the edge portion is liable to be damaged, probably because sufficient adhesion strength between the adhesive layer and the support is not obtained.

[0089]

According to the magnetic tape of the present invention, since the adhesion between the support and the adhesive layer is strongly maintained, the magnetic tape is repeatedly formed despite its relatively thick magnetic layer. Even after running, there is little peeling or damage of the tape edge,
Accordingly, high running durability is exhibited. In the magnetic layer, for example,
By adding the organic phosphorus compound, the precipitation of the powdery substance on the surface of the magnetic layer can be suppressed to a small amount even when the magnetic layer is stored for a long period of time, and therefore, a decrease in running performance due to this can be suppressed. For these reasons, the magnetic tape of the present invention can be advantageously used as a magnetic tape for recording computer data conforming to the DDS-2 type.

Claims (4)

[Claims] 1. An adhesive layer made of a polymer and a magnetic layer having a thickness of 1.2 to 2.5 μm containing a ferromagnetic powder and a binder are laminated in this order on one side of an aromatic polyamide support. A magnetic tape for computer data recording having a back coat layer on the other side of the support and having a total thickness of 4.0 to 8.0 μm, wherein the peel strength between the adhesive layer and the support is 95 g. / Cm or more, and the coefficient of friction of the surface of the magnetic layer of the magnetic tape after storing the magnetic tape at 60 ° C. and 90% RH for 30 days does not exceed 0.3. Magnetic tape for data recording. 2. An adhesive layer made of a thermoplastic saturated high molecular weight polyester containing an aromatic polyester and a ferromagnetic powder and a binder containing a binder having a thickness of 1.2 to 2 on one side of an aromatic polyamide support. A magnetic tape for computer data recording having a magnetic layer of 0.5 μm and a back coat layer on the other surface of the support and having a total thickness of 4.0 to 8.0 μm, wherein the adhesive layer, the support and The amount of the aromatic ester deposited on the surface of the magnetic layer after the magnetic tape has a peel strength of 95 g / cm or more and is stored at 60 ° C. and 90% RH for 30 days. Is not more than 1 mg / m ² . 3. The magnetic tape for recording computer data according to claim 1, wherein the magnetic layer contains an organic phosphorus compound represented by the following formula (I), (II) or (III). Embedded image [In the above formula, R ¹ , R ² and R ³ each independently represent a substituted or unsubstituted alkyl group, alkenyl group or aryl group, and M ¹ , M ² and M ³ each independently represent a hydrogen atom , An alkali metal atom or —N ⁺ (R) ₄ (R represents an alkyl group), and m, n and p each independently represent 1 or 2. ] 4. The adhesive layer has a thickness of 0.08 to 0.15 μm.
The magnetic tape for computer data recording according to any one of claims 1 to 3, wherein